It was down on the 82.7 percent figure for the previous quarter, and the same as the record low for the three months to September 2018.
A year ago, the treatment rate was 85 percent within 62 days. Only three of Scotland’s 14 NHS boards met the standard, Lanarkshire, Orkney and Shetland.
A separate target for 95 per cent of all patients to receive their first treatment within 31 days of a decision they need medical help was narrowly missed at 94.9 percent.
Scottish Tory health spokesman Miles Briggs pointed to the repeated failure to meet the 12-week treatment law, chronic staff vacancies, and the fact seven patients have died in the NHS Greater Glasgow and Clyde area since the start of the year after picking up hospital-acquired infections.
Mr Briggs said: “Jeane Freeman is a year into the job and things have only got worse. It’s been a year of failure. People who have been urgently referred for cancer treatment have never waited longer for their treatment to begin – that’s an abysmal reflection on her tenure.”
Gregor McNie, Cancer Research UK’s head of external affairs in Scotland, said: “Every quarter, figures emerge that show the NHS continues to be under immense strain.
“To have any chance of meeting its ambitions to diagnose cancer earlier, the Scottish Government needs to invest to ensure we have enough key cancer staff now and in the future.”
A spokesman for Ms Freeman said: “The overall number of cancer patients being treated within targets has increased on the same time last year, and it’s welcome that once a decision to treat has been reached, patients in Scotland wait on average five days for their first treatment.
“However, the Health Secretary has been clear that there are some patients waiting too long for treatment, and that’s why she brought forward our £850million Waiting Times Improvement Plan to drive improvements across all specialties, including cancer diagnosis and treatment.
“To ensure the highest standards of cleanliness are maintained, the Health Secretary commissioned an investigation from Healthcare Improvement Scotland (HIS).
“In turn, NHS Greater Glasgow and Clyde accepted all recommendations and developed their own action plan, which HIS are overseeing.”